1. Field of the Invention
This invention relates in general to web transport systems and, in particular, to a capstanless transport system for use in metering a web, such as magnetic tape, at constant speed and constant tension.
2. Description Relative to the Prior Art
What is perhaps the most relevant prior art for the present invention is the disclosure of U.S. Pat. No. 3,733,529, issued May 15, 1973, and the corresponding publications "Reel-to-Reel Drive Design for a Cassette Recorder" and "Audio Cassettes Become Digital with Novel Reel-to-Reel Drive" appearing in "Computer Design" of August, 1973, and in a trade publication, respectively. U.S. Pat. No. 3,733,529 teaches, in a capstanless magnetic tape transport system employing take-up and supply motors for driving, respectively, take-up and supply reels, the generation of a control signal corresponding to ##EQU1## where .omega..sub.1 and .omega..sub.2 represent the speeds of the take-up and supply motors, respectively. The signal ##EQU2## as taught in the patent, is equated with a signal representing a constant tape speed, the error therebetween being used to control the speed of the system `take-up` motor. Tape tension is maintained by applying to the supply motor a calculated variable "drag" signal that decreases with increasing supply motor speed. By virtue of the teaching of U.S. Pat. No. 3,733,529 the following system performance characteristics have been obtained, as noted in the publication "Audio Cassettes Become Digital With Novel Reel-to-Reel Drive":
(1) tape tension--.+-.0.75 oz. PA0 (2) tape speed variation--.+-.5% PA0 (3) flutter--3%.